The present invention pertains to a process for mixing and applying a flowable substance consisting of two components, and especially bone cement. More particularly the application relates to a two component calcium phosphate bone cement.
As is well known, bone cement is composed of a powdered component and a liquid component that react quickly after mixing. The finished mixture must therefore be processed as quickly as possible. The powdered component, which may be a combination of tetracalcium phosphate and dicalcium phosphate as disclosed in U.S. Reissue Pat. Nos. 33,161 and 33,221, the teachings of which are incorporated herein by reference, is usually supplied in sterile form in a blister pack or a bottle, e.g., with contents of 2 to 25 g. The liquid, e.g., a molar sodium phosphate solution, distilled water or sodium chloride solution is usually present in a sterile, plastic container, usually a disposable syringe having a volume of 10 cc. The two components are usually mixed in a vessel and processed from this vessel, e.g., by means of a syringe or the like. The mixing must be rigorous; on the other hand, the mixing time should not last too long.
The basic object of the present invention is to specify a process for mixing and applying a flowable substance, and especially bone cement, which can be carried out in an especially simple, effective manner.
This object is accomplished according to the present invention by the following steps:
The powdered component is filled into an injection syringe, which usually has a plunger at one end and a dispensing end, onto which a hollow needle is usually placed. However, the hollow needle is removed and, in its place, a suitable closing means, e.g., a cap is put on. Subsequently, the second, liquid component is filled into the injection syringe, and preferably via, a second syringe, filled with the liquid component via a hollow needled attached thereto. The first syringe is then closed with the syringe plunger under the load of sufficient air in the syringe cylinder. It is also conceivable for the two components to be already located in one syringe, but to be separated from one another by a separating wall. The separating wall is removed or made permeable for the mixing.
The syringe is then shaken rigorously for the purpose of mixing the components. Subsequently, the closing means, i.e. cap, is removed and a hollow needle is placed onto the first syringe, after which the flowable substance is then delivered at a desired site, e.g., at the bone being treated.
The present invention starts from the assumption that the liquid component is packed in a container, for example, in a disposable syringe, and can therefore be relatively simply injected into a syringe that contains the powdered component. This syringe is used as the mixing vessel. It is closed at the ends. It can be moved vigorously, therefore, e.g., even in a mechanical mixing device, so that rigorous mixing can be carried out within the shortest time.
The present invention also pertains to a mixing device, with which a flowable substance, consisting of two components, can be rigorously mixed in the shortest time, e.g., for the formation of a bone cement. Such a mixing device provides an injection syringe with a plunger and a closing device such as a cap on the front end as a mixing vessel for the components filled in. Comparable to the liquid component, the powdered component can likewise be packed in a syringe in sterile form. It is also possible, however, as described above, to fill the powdered component into the cylinder after the removal of the syringe plunger, after which the liquid component is then filled in as well. Subsequently, the plunger is introduced into the cylinder under the load of a sufficient clearance for mixing purposes. The mixing device also has a holder for the detachable holding of the syringe, as well as a mixing system, which imparts on the holder a movement that arises from the superposition of a rotatory and a translatory movement. The mixing system is set into operation by an input shaft, which is driven either manually or by the spindle of a rotating drive motor, e.g., a pneumatically or an electrically driven surgical machine or a separate electric motor. An input transmission is then preferably arranged between the spindle and the input shaft of the mixing system. The input transmission appropriately increases or decreases the speed, before it is transferred to the mixing system. The shaft of the input transmission has a corresponding mount for the drive spindle of the rotating drive motor, which may have a special attachment that can be plugged into the mount.
According to another embodiment of the present invention the holder for the injection syringe of the device according to the present invention is designed as a connecting rod of a connecting-rod drive. For this purpose, the end of the holder may be eccentrically articulated on a rotor, which is coupled with the output shaft of the input transmission, while the other end is mounted in a linearly movable manner.
After the mixing and removal of the syringe, the syringe can be actuated via a dispensing device. According to the present invention, such a dispensing device has a mount for an injection syringe with plunger, such that the dispensing end of the syringe is accessible by hand for the removal of a closing means or cap on the dispensing end and the attachment of a hollow needle. The dispensing device (not shown) which may be similar to a standard caulking gun and has a feed bar, which cooperates with the plunger end of the syringe and is actuated by a hand lever, whose movement is transferred to the feed bar via a transmission. Such dispensing guns have already become known for other purposes, e.g., for pressing sealing material or caulking out of a cartridge, which is inserted into a mount of the gun.
In the present invention, a secure mounting of the syringe in the holder consists of providing a holder having a channel in which the syringe is inserted. Moreover, the channel has, at intervals, transverse grooves, into which the flange of the syringe cylinder can be inserted. In this way, syringes of varying length may be securely mounted on the entire holder. For fixing the syringe to the holder, a web is preferably provided, which crosses the syringe and can be fixed to the holder by means of screws or the like, in order to fix the syringe cylinder in a clamping manner.